The present invention relates to a sonic absorption device for an air pipeline of an aircraft, which sonic absorption device comprises at least one curved pipe section whose respective interior wall is clad with sound absorption material, wherein within the curved pipe section at least one air guidance means is arranged for flow optimisation.
Air pipelines used in aircraft construction are subject to particularly stringent requirements relating to sound protection and flow dynamics. At the same time, air pipelines in an aircraft are to be dimensioned such that flow losses are kept to the minimum possible, for example in order to minimise the energy required for conveying the conditioned air. As a result of the confined space within an aircraft, air pipelines comprise a substantial number of curved pipe sections. In these positions preferably dispersion sound absorbers are used, because they are particularly efficient in these circumstances. Furthermore, the change in direction of the airflow results in turbulence, which among other things reduces the flow speed of the air.
For the purpose of dispersion sound absorption, usually in particular the curved pipe sections of the air pipeline comprise or are lined with a sound absorption material. Furthermore, in particular in the case of highly curved pipe sections, turbulence in the airstream occurs which has a negative effect on efficiency, with air guidance means counteracting said turbulence.
However, a combination of air guidance means and sound absorption cladding in a curved pipe section can have a negative effect on the efficiency of sound absorption. The reason for this is because, for example, two air baffles, arranged parallel in relation to each other, as air guidance means within a curved pipe section produce three separate channel sections which when individually considered, are not fully clad with sound absorption materials. In particular the middle duct, which is formed by two air baffles that are arranged at a distance from each other, is unprotected in this regard.
Attempts have already been made to counteract this problem by using an increase in the bending radius of the curved pipe section so that at the most one air guidance means within the curved pipe section is required. However, this measure requires more installation space within an aircraft, which design space is again at a premium. Furthermore, attempts have already been made to design air guidance means in the form of acoustic separators. An acoustic separator is an aerodynamically shaped air guidance means comprising a wing shape, with the interior space of said separator comprising a filling of a sound absorption material. The connection to the sound absorption material is established by way of conventional perforations of an extent of perforation of approximately 20%. The term “extent of perforation” refers to the area of the surface that is taken up by perforations. While such an acoustic separator itself acts as a sonic absorption device, due to the thickness of the acoustic separator, this solution, however, requires a correspondingly large installation space in the interior of the curved pipe section, which in turn increases the drop in pressure in a disadvantageous manner. Furthermore, it has been shown that an extent of perforation exceeding 10% in itself may form a source of sound.